Gas piston for operating automatic gun breech locks



GAS PISTON FOR OPERATED AUTOMATIC GUN BREEZCH LOCKS P. H. DIXON 3 Sheets-Sheet 1 Filed Dec.

Jizvenfor Paul H Dzxon y 9, 1951 P. H. DIXON 2,554,618

GAS PISTON FOR OPERATED AUTOMATIC GUN BREECH LOCKS Filed Dec. 16, 1946 3 Sheets-Sheet 2 4 inueniar 55 a 50 20 Paul H.Dz'xon 1y i hi Attorney y 1951 P. H. DIX-ON 2554;618

GAS PISTON FOR OPERATED AUTOMATIC GUN BREECH LOCKS Filed Dec. 16, 1946 s Sheets-Sheet 5 eeQ/Q I Fg I Hits C 64 3000 I sunsglu HAMTER I 2000 -PRsssuRE IN GUN BARREL BORE6O r Paul HDz'zorz 1000 5 'fiME AFTER IGNmoN IN SECONDS PRESSURE IN Pouu 0s FER SQUARE INCH Patented May 29, 1951 PaulH. Dixon, ltockfuord, 111., assignor by mesne a si nments, t heU ed Sta e of rt ta 'r'q ihaener A p ca ion semhe xl i d LIP-71952559 ,1 can 49719 This invention relates to ordnance and more particularly to gas operated automatic g ns of the type commonly-referred to as cannons.

It is desirable to reduce to a minimum the Weight and vibration of small cannons used in airplanes. Moreover, it is increasingly important to raise the cyclic rate of such cannon in View of the fact that an enemy'airplane is usually in the gunners sights 'for only a iew seconds at a time and during such time as many rounds as possible should be fired. In prior attempts to increase the cyclic rate of cannons it has been found that the harmonics of the moving parts of said cannons is such that not only the accuracy of -fire is reduced and the strain on the gunner is increased but also that such undesirable harmonics defeats to a considerable extent the attainment of the increased firing rate and has in some instances madeit dangerous to fire said cannons.

After a gun or cannon has been fired the breechblock or bolt of the cannon is commonly retained-in a locked position against recoil until pressure in-a bore of; a barrel ofthe cannon has dropped below a certain point, it being apparent that premature unlocking and 3 openingof the bolt-results in the loss of propellent force applied to the projectile and causes carbon depositsand sometimes-explosionsin the receiver. Moreover it has been found that when cannon are-used in small turrets, blowback gases should be kept at a minimum-thereby insuring against such gases polluting the air in the turrets and otherwise interfering with the comfort and safety of the gunners in the turrets. --In order to attain a high cyclic rateit is highly desirable that the -bolt, after beingunlocked, and parts associated with said bolt shall be moved in recoil and counter-recoil as fast as possible and shall be so constructed and mounted'for movement that vibration in the gun shall be reduced to a minimum.

It is an object of the present invention to provide agasoperated automatic cannon Whichwill fire at a rate greater than that ofcannons now in use and which when fired at such rate is smooth and effective in its operation.

"With the above object in-view and in accordance with a feature of the present invention, there is provided an automatic cannon coniprising a barrel having-a bore provided with a cartridge chamber, a bolt and associated parts movable to and from a battery position adjacent to the barrel, means for locking siaid bolt in battery position aud tor-unlocking said (bolt,

2 an expansion lchambe'r, .a passage extending from said expansion chamber to. a portion .of the bore located just forward 0f said cartridge chamber, and an actuating member .whicli'iis muvable in and lform's part of said expansion chamber. and which is .operatively connected to said locking and unlocking means, the construction of the passage, the expansion chain.- ber, other actuating .member "and .said .locking and unlocking means lbeinglsuch' that pressure .in the expansion chamber .caused by .g'ases .escap; ing into it :f-rom :the '.bore,' after increasing Jto a point at which it is approximately equal .to, the .pressure in the bore and having actuated said .means to .unlock said Jaolt, continues .-.to rise for a substantial periodto exert anincreasing force against .-.the bolt and parts associated with .the .bolt to. assist Jolowback action ofl'the case of the fired c artridge of said .g un rapidly to .move the bolt and parts associated there with :to recoiled positions. When the gun is mountedinsmallturretssuch as above referred to, the unlocking of the bolt is -preferably do layed sornewhat bi reducing the cross sectional area of said passage, the construction and a1"- rangernerrt being such that the} unlocking takes place when the residual gas ressure" in" the rqr .sz hergr is 2w sl d esidual P s ng h sh e i Raggqg A. W, l, r V

1 :1 qrder .t esu at r p ly in rec-0 1 a t lei. I the.v d creasing pressurein. said h ra. a d: here: afterttoocause pressure-of fees :in the T n-embers to increase to anoint in which bis tially reaterthan thatzin the barrel While-act: ing through said mechanism 7 against the. 1m.- locked boltieither' independently .iorv-inicooperae tionwithblowbackaction of the casellofflithe fired cartridge against the bolt to cause rapid recoil movement of said bolt.

By providing the illustrative construction the cyclic rate of cannon has been materially increased and said improved cannon when firing at or near its highest cyclic rate has not sufficient vibration to be objectionable.

The various features of the invention will be understood and appreciated from the following detailed description read in connection with the accompanying drawings, in which Fig. 1 is a side elevation of the illustrative gun, parts of which have been broken away and parts of which are shown in section;

Fig. 2 is an enlarged side view, partly broken away, showing portions of mechanism for unlocking a bolt of the gun;

Figs. 3 and 4 are full-size sections of the gun on lines IIIIII and IV-IV of Figs. 2 and 3 respectively Fig. 5 is an enlarged side view, partly in section, showing a bolt assembly of the gun locked in battery position.

Fig. 6 is a view corresponding to the rear portion of Fig. 5 showing portions of the bolt assembly unlocked, ready for movement in recoil;

Fig. 7 is an exploded view of the bolt assembly; and

Fig. 8 is a chart showing the gas pressure in a bore of the barrel of the gun and in operating chambers which will be described later, at different times after ignition of the cartridge in the With the exception of gas operated mechanism, which will be hereinafter described in detail, for unlocking a bolt or breechblock 20 (Figs. 1, 2, 5, 6 and '7), the illustrative gun is similar to the well-known Hispano-Suiza 20 mm. gun and comprises a cradle 22 upon which the gun slides to a slight extent in recoil and counterrecoil. The gun comprises a receiver 24 to the forward end of which is screwed a tube or barrel '26, and a recoil spring 28 (Fig. 1) mounted upon the barrel and having its front and rear ends in engagement with front and rear recoil spring seats 30, 32 respectively secured to the barrel and to a recoil housing assembly 33 fixed to a mounting bracket 35 bolted to the cradle 22.

Mounted for forward and rearward sliding movement in the receiver 24 is a breechblock or bolt assembly 34 (Figs. 1, 5 and 7) comprising the bolt 20, which has a longitudinal bore 36 (Fig. 5) for receiving a firing pin 38 (Figs. 5 and 7), a pair of bolt slides 40 (Figs. 1, 2, 5, 6 and 7) which are secured together by a key 42 extending through an elongated slot or recess 44 (Fig. '7) of the bolt 20 and which are slidable lengthwise on supporting faces 46 of the bolt, and a lock 48 a cylindrical forward end of which fits in a transverse groove 5|] (Figs. 1, 5 and 6) of the bolt and is constructed and arranged to secure the bolt in battery position. When the gun is in battery position the bolt 20 is held against a chambered cartridge 49, as best shown in Fig. 5, the slides 40 being in the forward positions relatively to the bolt, with the key 42 approximately in engagement with the forward end of the recess 44. When the slides 40 are thus positioned, recesses 52 (Figs. 1, 5, 6 and 7) in the slides 40 will have moved forward with relation to the bolt 20 into positions (Fig. 5) out of register with a rear portion 54 (Figs. 5, 6 and '7) of the lock 48, a rear beveled face 55 of which is then in engagement with a face 51 (Figs. 1, 5 and 6) of an abutment or key 56 secured to the receiver 24.

The slides 40 are constantly urged to their forward positions shown in Fig. 5 upon the supporting faces 46 with relation to the bolt 2|], by rods 45 (Figs. 5 and 7), which are surrounded by a slide spring 41, respective ends of each spring being in engagement with a head of its rod 45 and a respective lug 5| extendingfrom each side of the bolt.

It will thus be apparent that before the bolt 20 can be unlocked it is necessary to move the slides 40 into such positions that the rear portions 54- of the lock 48 are in register with and can be moved into the recesses 52 of the slides 40 to permit'said lock to be raised out of engagement with the key 56, as shown in Fig. 6.

The barrel 26 is provided with circumferentially spaced gas ports or orifices 58, 58a just in front of a cartridge chamber 59 of a bore 60 of the barrel and are spaced equal distances from a vertical plane 6| through the bore axis of the barrel. (See Fig. 3.) In communication with the ports 58, 58a are ports 62 which are formed in a block 63 secured by tap pins 6'! (Fig. 3) to the barrel 26 and which communicate with cylindrical chambers 64 (Figs. 2 and 4) respectively formed in the block. The gas ports 58a which are of a diameter of approximately and are smaller than the ports 58, 62 are formed in a silver heat dissipating plug 65(Figs. 2, 3 and 4) fitting in a recess 66 of the barrel. The ports 58, 58a and 62 collectively may be referred to as a gas passage which extends between the bore 60 and one of the chambers 64. The recess 66 may also be described as an enlarged portion of a passage in the gun barrel, the heat dissipating plug 65 fitting in said enlarged portion and having said restricted orifice 580. which forms part of and connects, spaced portions of the gas passage extending from the bore 60 to one of the chambers 64.

slidable in each of the chambers 64 is a hollow piston or actuating member 68 (Figs. 2, 3 and 4);

a head 70 of which is arranged adjacent to an associated slide rod 12 mounted for reciprocation in a guideway 14 (Figs. 2 and. 4) of the receiver 24.

Assuming that the gun has just been fired, a projectile 16 of the cartridge moves forward in the bore 66 and passes the gas ports 58, portions of the burnin and expanding gases passing through the gas passages formed by said ports 58, 58a and 62 into the chambers 64. Such gases at that time are only partially burned and therefore, as they continue to burn, such gases increase the pressure in the chambers 64 causing the pistons B8 to move rearward. At the time the projectile 16 leaves the barrel, as represented by point on the gas pressure-time after ignition curve on the chart shown in Fig. 8, the gas or powder pressure in the bore 69 of the barrel 26 is slightly greater than the gas or powder pressure in the chambers 64 but at such time the pressure in the bore is dropping rapidly. At the time represented by point 82 (Fig. 8) the increasing pressure in the chambers 64 is equal to the pressure in the bore 60 and thereafter continues to increase, the peak portion of the gas pressuretime after ignition curve in the chamber lying outside the superimposed gas pressure-time after ignition curve of the bore of the gun barrel. Each of the ports 58a is of suitable size to restrict to a considerable extent the flow of gases from the expansion chamber 64 back into the bore,

thereby insuring the availability of an expansible the result that-eas est pist'his betwe n the sl de. actuatin rods-.12 and :theforward ends of the slides 140,1 rearward pressure. is exertedagainst said slides, WhileLthe projectile 76 is moving along the bore an of the barrel 26 the pressure in said bore is very high and the pressure exerted by the case of the fired cartridge against the bolt 20 causes the lock 48 to be forced with very heavy pressure against the abutment 56, said lock being forced by the reaction of the abut-ment 56 with considerable pressure against the slides 40 with the result that said slides are forced upward with substantial binding pressure against longitudinal guides 83 (Figs. 1 and 2) of the receiver 24. During the time that the projectile 16 is moving along the bore 60 of the barrel 26 pressure in the chambers 64 increases as shown by the gas pressure-time after ignition curve of said chambers. At the time of muzzle contact of the projectile 76 the pressure in the barrel bore 60, which pressure reaches a maximum of 50,000 pounds per square inch, will have been reduced to approximately 5,400 pounds per square inch, for example, the pressure in the chambers 64 at that time being high enough to have moved the rods 12 rearwardly approximately /2 inch and the slides 40 approximately 1 inch, the bolt lock 48 at such time being about ready to be forced into the recesses 52 of the slides to its position illustrated in Fig. 6 to permit said lock to be cammed up by the key 56 into the recesses 52 so that the lower surface of the lock can ride rearward over the upper surface of the key along guides (not shown) in the receiver.

When the bolt 20 has been unlocked blowback action of the case of the cartridge in the bore 60 upon said bolt 20 causes recoil movement of the bolt in the receiver 24 against the action of driving and bufier springs 84 and 86 respectively (Fig. 1). Because of the fact that the ports 58a of the heat dissipating plugs 65 are small and the gases which are in the chambers 64 are still burning and cannot readily escape back into the bore 60, such gases continue to increase in pressure in the chambers to attain a pressure of approximately 4,600 pounds per square inch indicated by the peak portion 88 (Fig. 8) of the gas pressure-time after time ignition curve of said chambers. 7

After the slides 40 actuated by the pistons 68 have moved rearward to the proper positions to permit the bolt 20 to be unlocked, the slide moves approximately an additional against the action of springs 41 until their key 42 engages the rear end of the elongated slot 44 (Fig. 7) continued rearward movement of the slides of approximately l-t" under the action of the pistons 88 imparting momentum in recoil to the bolt 20 and causing, in combination with some blowback action of the case of the fired cartridge against the bolt, the rapid movement of the bolt and its associated parts in recoil. Recoil movement of 6 theislides12isilimited-by engagement of rear ends ofithe slides with shoulde s 33.9. (Fig. 2) of the receiver 24,, the heads 70 of the :pistons 68 atsuch time being in engagement with surfaces 9| (Fig. 4) .of the receiver 24.

When it .is desired to delay the unlocking of theibolt 2E] until the pressure in the bore 69 of the barrel 26 has been reduced to a minimum or has been :entirely dissipated, the cross sectionalareas. of the gas portsifida are reduced with the result that a pressure-time after the ignition curve taken in the chamber 66 will be somewhat similar to. that shown in Fig. 8 but will have a peak which is lower than and is arranged to the right of the peak portion 88. With such construction the bolt 29 will not be unlocked until the residual pressure in the barrel bore 60 is quite low and by the time the case of the cartridge has been Withdrawn sufficiently to permit the flow of gases from the spent cartridge into the receiver the pressure in the bore of the barrel will be practically dissipated. As above stated, by further restricting the cross sectional areas of the ports 58a, the unlocking of the bolt 20 may be delayed until the pressure in the bore 66 of the barrel 26 has been entirely dissipated. It has been found that there is sufficient expansive force left in the chambers 64 after the dissipation of the pressure in the bore 60 of the barrel 26 to maintain a high even rate of fire.

As the bolt assembly 34 is moved in recoil the following round is delivered to the receiver 24 and as said assembly moves forward in counterrecoil under the action of bufier springs 8 86 the cartridge is chambered. After forward movement of the bolt 20 has been arrested, the slides 50 under their forward inertia and the action of the springs 'll move forward with re lation to the bolt 20 until the slide key 42 engages the forward end of the slot 54 in the bolt. In order to insure against the bolt 20 and the slides 40 bounding back out of battery position after their cartridge chambering movement is checked, inertia blocks 96 (Figs. 1, 2 and 5) are mounted in the slides. During forward move ment of slides 46 upon the bolt 29 the lock 13 is cammed down by the slides 40 into engagement with the key 55 to lock the bolt assembly 345 against rearward movement. The firing pin 38 which is cocked during its recoil movement with the bolt 20 is then released to fire the gun to start the operation of another cycle such as above described.

Having described my invention, what I claim .as new and desire to secure by Letters Patent of the United States is:

In an automatic rapid fire gun having a barrel including a cartridge chamber in the rear portion of its bore, a longitudinally reiprocable breechbolt closing the rear end of said chamber when said breechbolt is in forward position, means releasably locking said breechbolt in forward position, means forming a gas cylinder in fixed parallel radially-oifset relation with said cartridge chamber, said cylinder having its forward end closed, a restricted gas passage from a point in the bore of the barrel immediately forward of the cartridge chamber, through the wall of the barrel into said gas chamber, a tubular piston closed at its rearward end and slidably fitting said cylindrical gas chamber, said piston having an enlarged head externally of said cylinder comprising stop means limiting the forward reciprocation of said piston, the open forward end of said piston when in forwardmost position being iearwardly of the opening of said gas pas-"- sage into said cylinder, a slide reciprocable rearwardly to release said breechbolt locking means and having its forward end positioned for engagement and movement by said piston in response to rearward reciprocation thereof following the firing of a cartridge in the cartridge chamber, and stop means restricting rearward reciprocation of said piston to approximately one-half its length, said cylinder having a length 19 2,409,225

substantially twice the length of said piston.

PAUL H. DDION.

REFERES crrnn' The following references are of record in the file of this patent:

UNITED STATES PATENTS France Dec. 23, 1940 

